What a Negative Air Pressure Test Will Tell You
Negative air pressure is formed when more air is exhausted from your home than is brought in to it. Typically, this is due to a home's envelope being too airtight....it's like the house is "gasping" for air. It seems somewhat ironic that a house that has been made airtight to save energy should now be loosened up to become healthy, but that is, in fact, what is needed.
Houses Need to Breathe!
There are appliances such as bathroom fans, range hoods and clothes dryers pushing air out of your house. The result of this creates negative air pressure in the house which means the house becomes more interested in trying to suck air in than pushing air out. Your house will try to draw air in from the easiest place which will be the existing flues of the furnace, wood stove, fireplace and gas water heater. When this happens, carbon monoxide is being forced in to your home and indoor air quality is compromised.
Carbon monoxide is an odorless, tasteless gas that is toxic. It is a by-product of the incomplete combustion of fuels such as propane, wood, oil, gasoline and natural gas. Exposure to carbon monoxide can cause flu-like symptoms (headache, nausea, fatigue, dizziness, disorientation) and even death. Every home should have at least one carbon monoxide detector as well. If you don't have one, make the small investment.
Signs Your Home May Have Negative Air Pressure
A rush of air or draft when opening an exterior door
A lack of fresh air, a musty smell or lingering odors around the house
Mold, mildew, moisture or condensation around windows or on walls
Back drafting of combustion appliances such as the fireplace, wood stove, gas water heater or furnace
Eliminating Negative Air Pressure
Removing negative air pressure requires that you bring in "make-up" air from the outside in a controlled manner. A licensed HVAC contractor can help you determine if you need additional make-up air and how to best introduce it into your home. One method is through the use of mechanical ventilation. With this method, ducts and fans are used to bring new air into the home. Mechanical ventilation systems also allow for a constant flow of outside air into the house which is preferable to relying on outside air entering the house through foundation cracks, doors, windows, the garage, etc.